Bizarre cause of air suspension failure...

[Ozjood]

Hi Folks,

I don't know if any of you have encountered this situation before - it was incredibly frustrating at the time until the cause was established...

My wife and I bought a 2005 Discovery 3 HSE V8 in June 2011. To date its been great, other than encountering a few hassles when electric brakes were fitted (the causes being a combination of the installers wrongly wiring the Tekonsha P3 unit into the car, and a mobile phone being placed too close to the unit itself).

All was well, until I received the dreaded 'Suspension Fault - Normal Height Only' message upon starting one afternoon. I kept an eye on things but within a day it had progressed to the blunter message of 'Suspension Fault'. It was also evident that the compressor was not operating. Grumbling, I bit the bullet and ordered a new compressor from Paddock Spares in the UK, whose prices were certainly more reasonable than Australian vendors. By this time the Landie had sunk on its suspension. Rather than attempt the job at home with only car-spec jacks and ramps (a lesson has been learnt there!) I had the Discovery put on a flat bed truck to be attended to by a mechanic I trust.

Fitting the new compressor was a doddle, however on starting the Discovery rose only partially, the compressor working for a few seconds, then shutting off. New fuse and relay had been fitted, and they were intact. After another effort, and getting the same result, my mechanic shut the engine off and heard the sound of an air leak from the front left corner. After stripping away the wheel well covers the offending air hose was located.

Now this might not seem all that unusual, but the hose - aside from being split - was also sticky, perished and smelling of battery acid. Interestingly, this damaged portion of air hose was next to what appeared to be the battery vent tube. I also recalled that a new battery had been fitted to the Landie about 10 days before our purchase. All I can surmise is that either the previous owner or the dealer had tried to charge up the old battery, and either overcooked it (sending battery acid down the vent tube onto the suspension line), or found the battery to be beyond redemption and overturned it in trying to remove the battery out of the engine bay. Certainly, there was evidence of a fair bit of acid having got into the area, with lots of bicarbonate of soda now being needed to clear this mess up.

Anyway, all was well after removing the offending section of hose and fitting a repair section using high pressure hose and appropriate fittings. It goes without saying that the battery vent hose has been re-routed too, and I'll be checking whether the old compressor is in fact OK...

Cheers,

Jude and Andrew Matusiewicz
2005 Discovery HSE V8

[DoctorJ]

It would be interesting to hear if the compressor was faulty at all, I was told that my compressor may be faulty as it was very loud, but it turned out that the bracket needed replacing and that was it (it is now substantially quieter), would be interesting to know how many compressors get replaced due to their bad rap unnecessarily.

Cheers
Julian

[LRTech23]

The compressor probably burnt itself out trying to pump up the front left.

The compressor should run to at least fill itself up.

[Graeme]

The compressor should run to at least fill itself up.
What do you mean by this?

[101RRS]

What do you mean by this?

Maybe fill the air tank up????

[LRTech23]

As far as I'm aware there's a reservoir that the compressor replenishes.

[Ozjood]

Hi Folks,

Yes, there is a reservoir holding pressurised air.

In trying to understand what was afflicting our Landie, I came across the following.

http://www.disco3.co.uk/gallery/albums/userpics/15405/Land%20Rover%20factory%20D3%20air%20suspension%20d escription.pdf

Quite interesting reading!

As to whether the old compressor burned out, I'll find out when I test it. I'd be surprise if it has, I would have thought that the 60A fuse for the air suspension would have blown beforehand (it hadn't).

Cheers,

Andrew Matusiewicz
2005 Discovery 3 HSE V8

[Graeme]

As far as I'm aware there's a reservoir that the compressor replenishes.
Ah yes, but only after having completed any raising requirements.

[LRTech23]

Yes Graeme that is absolutely correct.

And OzJood, they burn themselves all the time, trying to fill up the reservoir they can become too hot and just die. I'd say that 90% of the compressors that we replace have burned out.

I've never seen a blown fuse. Simply because it's not due to an excess amount of current (it could well happen I've just never seen it), the compressor just works itself too hard and the motor burns out, simple as that.

[Geedublya]

That's strange as it has sensors on the head and brushes to detect an over temperature situation. When the cpu detects an over temperature it stops the compressor and displays a warning.

If there was an air leak and it was running a lot more than usual I can imagine it would wear out the brushes or piston sealing faster though.

[spudboy]

On my L322 "Full Fat" Range Rover I've read of an error message something like:
- Compressor running but no pressure increase
and the ECU will stop the compressor from burning itself out in this situation.

I'd be guessing that a newer D3/D4/RRS will have similar logic.

[LRTech23]

Well, I work for a dealer and they do all the time. That's what we diagnose them as and that's what it says on the warranty report.

Just trying to give you the information as it is.

[Ozjood]

Hi Folks,

It may well be that the old compressor has cried enough and died. As soon as I get a chance to check out the old unit, I'll let you know.

That said, the real reason for my post was to highlight the seemingly freakish nature of the hose being damaged... :eek2:

Cheers, :twobeers:

Andrew Matusiewicz
2005 Discovery 3 HSE V8 :TakeABow:

[LRTech23]

Yeah, at least you sorted out the issue, let us know what happened if you can.

[clubagreenie]

Sounds like a supplementary pressure switch, wired into a 555 timer, on the line to the reservoir from the compressor (after any check valve between the two) needs to be fitted to switch the compressor of if it's run for X amount of time without achieving a pre determined rise in pressure in a pre determined amount of time.

But knowing modern designers its probably all internal. But could it be done with a replacement compressor? What pressures are needed for the system to run/lift the car?

[spudboy]

This is applicable to the L322. Would suggest D3/D4 would be similar:

Compressor Disabled
Operation of the compressor is prevented by the ECU in the following conditions:

1. Temperature sensor on compressor indicates compressor is overheated. The ECU will allow the compressor to be run up to 110 degrees C for height adjustments but only up to 100 degrees C for reservoir filling.

2. System pressure sensor indicates pressure exceeds 13.7 bar (200 psi).

3. Timeouts: The ECU will only allow the compressor to run continuously for a maximum of 3 minutes regardless of temperature or pressure. If it is attempting to fill the reservoir it remains off for 3 minutes before resuming, but if it is just regulating system pressure it only takes a 20 second break.

[clubagreenie]

So if we had:



A compressor that could push just over 200psi (probably look at 250).
An external, maybe larger reservoir for less cycling.
Temp controlled running so it will run within pre-determined limits of temp of compressor.
Time controlled running based on a known value of x min to fill empty reservoir and current volume of reservoir. To establish with other inputs is pressure loss has occurred and where.



It would be good?

[LRTech23]

Yeah, if you wanted to do it yourself, sounds expensive though, Land Rover would meet do it.

[clubagreenie]

Development of chip programming, 1 slab, reservoir 2 slabs, compressor couple hundred.


Land Rover would meet do it. WTFBBQ?

[CaverD3]

Existing compressor is capable of 240 psi.
Extra resevoir is easy. OEM tank on other side, it has been done.
An external compressor would have to have a dryer and be changed regularly.
Ther new OEM compressor may have a bigger brother?

[LRTech23]

Development of chip programming, 1 slab, reservoir 2 slabs, compressor couple hundred.

WTFBBQ?

Haha yeah I meant to say never, not meet. Damn iPhones!

[Graeme]

So if we had:



Time controlled running based on a known value of x min to fill empty reservoir and current volume of reservoir. To establish with other inputs is pressure loss has occurred and where.


It would be good?
The suspension ecu already has plausibility checks for airspring height increase and reservoir pressure increase for compressor run time that prevent the compressor from running without sufficient effect.

The only modification I'd do is to fit a larger or 2nd reservoir now that the reservoir pressure has been lowered from its original design pressure in order to extend compressor life, which is probably more due to a dryer that is too restrictive and too easily clogged if not serviced or replaced regularly.

[clubagreenie]

I could possibly source 20lt (water capacity @ 1atm) cylinders for reservoirs for about $40 or $50.

[sniegy]

Do you have a physical size of the cylinder LxWxH
Cheers

Sent from my iPad using Forum Runner

[CaverD3]

20l are usually 200mm. OEM is 115mm. You could get a 120mm to fit on the opposite side.

Boss Alloy 15 Litre Air Tank with 5 Ports - Air Tanks - Air Comp & Acc (http://www.4x4andcamping.com.au/index.php/air-compressors-accessories-1/air-tanks/boss-alloy-15-litre-air-tank.html)

Could work if dia includes legs otherwise it is
three of these:

Boss Alloy 3 Litre Air Tank with 3 Ports - Air Tanks - Air Comp & Acc (http://www.4x4andcamping.com.au/index.php/air-compressors-accessories-1/air-tanks/boss-alloy-3-litre-air-tank.html)

[clubagreenie]

Sorry that should have read 20cuft @ 220bar, 4lt.

About 100mm and 400 to 500 long.

[CaverD3]

Is that max or working pressure?

[clubagreenie]

Thats working pressure, test pressure of approx 350bar by memory.So you could get it filled to max presure, then regulate it and not have to run the compressor for a while....

[CaverD3]

The working pressure of the EAS is over 200psi (13.8 bar)so you would well within the pressures.
Would easily fit a couple on the opposite side. Could attach a compressor with a dryer for emergencies and could be used for tyres as well.
Can't afford the mod at he moment but would be useful as I have an air off kit which just works for airing back up from off road to on road before it runs out of puff.
Are they a normal air cylinder with one outlet or a tank with multiple?
Maybe mods should move some of hese post to another thread?

[rufusking]

Might want to check you Maths. 200psi isn't 138 bar. Closer to 13.8 bar.

[CaverD3]

Sorry senior moment. :angel: 3.8 bar. Well within still. edited it

[clubagreenie]

It's actually a small scuba cylinder. I can get them after they have failed their annual hydrostatic test. The test involves filling with water and pressurising to test pressure and measuring diameter expansion along the length as well as any change in length. Failure for high pressure use is failure, but for use at up to 500psi I would not be in the slightest bit concerned.

Although I have seen a failure during high pressure fill at a scuba shop where the bottom blew out of a cylinder. Apart from a few people coming out with bleeding ears, it landed across the road (after punching through the first floor (concrete) and out the roof) into Coogee oval some 4 foot down.